The Research Methods Core, following the principal goals of the CIDAR Program Announcement, aims to foster fuller integration of innovative basic research methods into the clinical assessment and therapeutics arena. Supporting each of the 4 research projects and advancing the overall goals of the CIDAR, the RMC has 3 specific aims comprising both service and scientific missions: Specific Aim 1: Implement cognitive and neurophysiological assessment methods across projects, guaranteeing uniformity and high quality in data collection, recording, and analysis;Specific Aim 2: Collect data on a reference sample of healthy volunteers matched to the combined demographic characteristics of projects I and IV (thereby also matching project III); and Specific Aim 3: Further refine measures using psychometric methods and modeling, and combining information across projects, to inform the development pipeline for novel assays and biomarkers of cognitive control that will be useful for future therapeutic trials and translational research. Assay refinement will rely on determinations of: (a) discriminant validity (with respect to the diagnosis of ADHD);(b) construct (nomothetic) validity for combinations of indicators;(c) concurrent validity with respect to neural systems effect;and (d) exploratory cross-validation with respect to treatment effects. The RMC is staffed by a team of experts in neurocognitive assessment, neurophysiological assessment, psychometrics and measurement methods, with extensive experience specifically in the implementation of cognitive and neurophysiological service core functions in NIMH Centers, and in the scientific integration of high-dimensional, multimodal data sources to enable inferences about underlying neural systems processes affected in cognitive control disorders. The long-term aims of the RMC include development and deployment of integrated "panels" of behavioral and neurophysiological assays, cross-validated in translational research, which can be used in clinical trials of next-generation psychopharmacological and behavioral interventions for pediatric disorders of cognitive control. The RMC will also disseminate these novel assays and analysis methods freely to the scientific community.